1. Field of the Invention
This invention relates generally to verifying rewritable optical disc media, and more particularly to verifying sectors of optical discs to check for defective sectors prior to storing data on the sectors of optical discs.
2. Description of the Related Art
Consumers are increasingly demanding storage media which have greater storage capabilities. In response to these demands, retailers have started manufacturing optical discs such as rewritable compact discs (CD-RW) that have increased storage capacity in comparison to other storage media. Optical discs store information on tracks that spiral around the center of the disk. The spiral contains sectors to which data is written and stored. When optical discs are purchased by consumers, certain defects may exist on the optical disc itself. These defects may be the culprit of mishandling during the manufacturing phase of the optical disc, drive to media compatibility, imperfection in the material of the optical disc itself or any other manufacturing error. The defects affect the storage capabilities of the optical disc in that certain sectors on the optical disc are not capable of storing information.
For packet writing, data is commonly written to a disc onto one track. Groups of sectors are then written to the track. However, before the groups of sectors are written to the track, measures must be taken to verify the optical disc in order to determine what sectors are defective to prevent writing to those sectors and potentially losing the data written to those defective sectors.
In order to determine which sectors on a optical disc are defective, the optical disc is subjected to a verification process. Current types of verification processes write data to the optical disc and then reads are performed to the written sectors to determine if particular sectors on the optical disc are defective. In one example verification process, 0's are written to the sectors and then reads are performed to determine if 0's are read back. If 0's aren't read back from a sector, the sector will be flagged and the file system of the optical disc will be updated to reflect that data should not be written to that particular sector. While this method ensures that data will not be written to defective sectors, the process is very time consuming. Using a 2× writing operation and a 6× reading operation, the verification operation can take anywhere from 50 to 90 minutes to complete. This amount of time makes optical discs and more particularly CR-RWs an unattractive option to those desiring to quickly store data to new discs. Due to the amount of time required to do verification, some software packages provide the option to skip verification altogether.
Another method used for verifying sectors on optical discs involves only verifying a small group of sectors and then writing user data to the verified sectors. This is an alternative to verifying the entire disc before allowing user data to be written (i.e., as described above). While a next set of sectors are verified, user data is allowed to be written to the verified group of sectors. Of course, user data cannot be written to the entire optical disc, just areas that have been verified. Under this scheme, additional sectors are written to keep track of what sectors have been verified. Nonetheless, this process is also time consuming because a user must wait for the verification before user data may be written to the disc. Also, extra storage capacity is occupied by the sectors that keep track of which sectors have been verified. This, as can be appreciated, uses up space that would otherwise be available for user data.
In view of the foregoing, there is a need for a method to verify optical discs that is less time consuming than prior art methods. This verification method should also allow user data to be written immediately to an optical disc as the optical disc is being verified.